tree 67d16bf4e889e6b36ea7d906d78ab91676931b12
parent edb621b84aa0892ca729dfbf6179be528377dcb5
author Gilles Peskine <Gilles.Peskine@arm.com> 1579551170 +0100
committer Simon Butcher <simon.butcher@arm.com> 1584116625 +0000

mpi_copy: make the 0 case slightly more robust

If Y was constructed through functions in this module, then Y->n == 0
iff Y->p == NULL. However we do not prevent filling mpi structures
manually, and zero may be represented with n=0 and p a valid pointer.
Most of the code can cope with such a representation, but for the
source of mbedtls_mpi_copy, this would cause an integer underflow.
Changing the test for zero from Y->p==NULL to Y->n==0 causes this case
to work at no extra cost.